Fracture simulation of cold roll forming process for aluminum 7075-T6 automotive bumper beam using GISSMO damage model

This study deals with cold roll forming process of automotive bumper beam with aluminum 7075 T6. The simulation method for predicting crack during roll forming process of aluminum 7075-T6 automotive bumper beam was developed. Practically W shape bumper beam was tried out cold forming by 12 stages roll forming process. The cracks were observed at some bending regions. Through the numerical analysis result, the cause of crack occurrence and its propagation was judged as caused by multi-axial strain state of coil during roll forming process. So, GISSMO damage model (Generalized Incremental Stress State Dependent Damage model) was adopted for the fracture simulation. In order to find GISSMO damage parameters, tensile tests were conducted on various load paths to derive fracture strains according to triaxiality. Numerical analyses for the tensile test were conducted to correlate element deletion along to element size with load drop obtained by experiments. As results, predicted cracks through the roll forming simulation with GISSMO damage are close to actual try-out result. Besides, a roll design remedies for preventing crack were suggested.